1. Field of the Invention
The present invention relates to a hydraulic pump unit of variable displacement type disposed away from a pair of hydraulic motor units which are capable of being independently arranged, the hydraulic pump unit fluidly-connected to the pair of hydraulic motor units so as to change the outputs of the pair of hydraulic motor units in both forward and reverse directions.
Also, the present invention relates to a working vehicle provided with a pair of hydraulic motor units, a hydraulic pump unit of variable displacement type and a travel operation mechanism capable of being manually operated.
2. Related Art
It has been conventionally known that a hydraulic pump unit of variable displacement type and a hydraulic motor unit, which are fluidly-connected to each other so as to form an HST, are configured to be capable of being independently arranged.
The hydraulic pump unit and the hydraulic motor unit are particularly useful in a working vehicle needing to provide a space between a pair of driving wheels so as to stabilize the body posture at the time of turning such as a mower tractor capable of turning in place (zero turn) (for example, see U.S. Pat. No. 6,425,244).
The hydraulic pump unit of variable displacement type is provided with a hydraulic pump body operatively rotated and driven by a driving source and a capacity adjusting mechanism for changing the capacity of the hydraulic pump body. The output of the hydraulic motor unit can be changed by operating the capacity adjusting mechanism.
However, in the conventional hydraulic pump unit of variable displacement type, since the capacity adjusting mechanism is merely connected to a manual controlling member such as a traveling lever erected from right and left side floors of a driver sheet via a machinery link mechanism, large manual operation power and manual operation amount are required for the travel operation of a vehicle.
Since the large manual operation power and the manual operation amount are required for the operation of the capacity adjusting mechanism, it is difficult to miniaturize the controlling member.
The present invention has been accomplished in view of the prior art, and it is an object of the present invention to provide a hydraulic pump unit of variable displacement type capable of reducing the manual operation power and the manual operation amount for changing the capacity of the hydraulic pump body.
It is another object of the present invention to provide a working vehicle provided with a pair of hydraulic motor units for respectively driving a pair of driving wheels, a hydraulic pump unit of variable displacement type having a pair of hydraulic pump bodies respectively fluidly-connected to the pair of hydraulic motor units, and a controlling member for changing the supply-discharge oil amount of the pair of hydraulic pump bodies and capable of being manually operated, the working vehicle capable of miniaturizing the controlling member.